Crookshanks waits until Jim can claim the weapon that was given to his mistress by the other Jim who visits the Nexus. He knows that the human will know how to use it.

Then he heads off, towards the centre of the Nexus, where all the doors are located. With ease, he leads Jim to a door that looks like it belongs to an ancient castle. There is a soft glowing green light underneath the door.

He scratches at the door. Twirls around in a circle. Then scratches at the door again.

A tiny little kitty-door opens for him. He meows at Jim, as if asking him to wait please, before disappearing into the kitty-door.

The green glow gets brighter for a moment. Then the door slams open, Hermione wielding her wand to hold back a spell as she backs out of the door. Crookshanks keeps by her feet, watching carefully. "Expecto Patronum!" She casts, and the otter appears before her, swirling around her wand to collect more and more light. Then the otter swims forward, pushing forward a shield of light with it, pushing the spell even further back from the door.

"Jim!" Hermione sees that he is standing there, from the corner of her eye. "Close the door!"